Ok, so you start with three sons of Noah who can form 3 couples >
Roughly, in the first fifteen years, a baby or so a year, three couples can yield > at least 40
after year thirty, 20 couples from those forty babies in fifteen more years can each have at least ten babies > 200
after year fifty-five those 100 couples > 1,000
after year 70, 500 couples in fifteen years can each make ten babies > 5,000 babies
after year 85, 2,500 couples from those babies > 25,000
after year 100, 17,500 couples > 175,000
after year 115, 87,500 couples > 875,000
after year 130, 437,500 couples > 4,375,000
after year 145, 2,187,500 couples > 21,875,000
after year 160, 10,937,500 couples > 109,375,000
after year 175, their 54,687,500 > 546,875,000
after year 190, 273,437,000 couples > 2,734,370,000
This is by only about 200 years after Noah, with couples breeding about ten kids each over fifteen years for each couple.
Roughly, every fifteen years, like this, the population is five times as much as fifteen years ago; so I consider it would go like this >
year 205 > 10 million
year 220 > 50 million
year 235 > 250 million
year 250 > about a billion
year 265 > 5 billion
Didn't someone say we have about four hundred years or so? We're not at year 300 yet.
And this is with each couple having fifteen years to make ten babies, with no twins or octuplets
year 280 > 25 billion
year 295 > 125 billion
year 310 > 625 billion
year 325 > I think we have enough